Power supply device

ABSTRACT

In a power-supply device, a FET passes or blocks a current flowing from one side in a power-supply circuit. A current sensor detects a current flowing into the FET. A FET is coupled to the FET, and passes or blocks a current flowing from another side in the power-supply circuit. A current sensor detects a current flowing into the FET. A junction couples a load unit at a point between the FET and the FET. In each of switch units, a CPU controls the corresponding switch unit of the power-supply circuit based on the detection result detected by the corresponding current sensors.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims priority to and incorporates by referencethe entire contents of Japanese Patent Application No. 2019-008971 filedin Japan on Jan. 23, 2019.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to power-supply devices.

2. Description of the Related Art

Japanese Patent Application Laid-open No. H10-262330 discloses, asconventional power-supply devices, a power-feeding device for vehiclesthat supplies power to electrical parts installed in a vehicle, forexample. Such a power-feeding device for vehicles includes a pluralityof power distributors that distribute power to the electrical parts, afeed line that couples each power distributor in a loop shape, a batterythat supplies power to each power distributor via the feed line.

For example, at the time of the occurrence of faults, such as a shortcircuit, the above power-supply device for vehicles described in PatentDocument 1 shuts off the power-supply distributor to prevent such afault. However, there is room for further improvement in this point.

SUMMARY OF THE INVENTION

The present invention is devised in view of the above, and the objectthereof is to provide a power-supply device capable of improving faulttolerance.

In order to solve the above mentioned problem and achieve the object, apower-supply device according to one aspect of the present inventionincludes a power supply that supplies power; a power-supply circuit thatis a circuit coupled to the power supply and includes a plurality ofswitch units, the switch units passing or blocking a current of thepower supplied from the power supply; and a controller that controlsturning on/off the switch units and controls the power-supply circuit;wherein each of the switch units include: a first switch having a firstcurrent blocker that passes or blocks a current flowing from one side inthe power-supply circuit and a first current detector that detects acurrent flowing into the first current blocker; a second switch having asecond current blocker that is coupled to the first current blocker andpasses or blocks a current flowing from another side in the power-supplycircuit and a second current detector that detects a current flowinginto the second current blocker; and a junction that couples a load unitat a point between the first current blocker and the second currentblocker, and in each of the switch units, the controller controls thepower-supply circuit based on detection results detected by thecorresponding first current detector and second current detector.

According to another aspect of the present invention, in thepower-supply device, it is preferable that the switch unit to becontrolled includes a communication unit to be controlled that iscapable of communicating with the switch unit to be uncontrolled, thefirst current detector to be controlled detects an amperage of a currentflowing into the first current blocker to be controlled, and a firstcurrent direction to be controlled that is a direction of the currentflowing into the first current blocker to be controlled, the secondcurrent detector to be controlled detects an amperage of a currentflowing into the second current blocker to be controlled, and a secondcurrent direction to be controlled that is a direction of the currentflowing into the second current blocker to be controlled, thecommunication unit to be controlled receives a first current directionto be uncontrolled that is a direction of a current flowing into thefirst current blocker of the switch unit to be uncontrolled, and asecond current direction to be uncontrolled that is a direction of acurrent flowing into the second current blocker of the switch unit to beuncontrolled, and the controller controls turning on/off the firstcurrent blocker to be controlled based on an amperage of the firstcurrent blocker to be controlled, the first current direction to becontrolled, and the second current direction to be uncontrolled, andcontrols turning on/off the second current blocker to be controlledbased on an amperage of the second current blocker to be controlled, thesecond current direction to be controlled, and the first currentdirection to be uncontrolled.

According to still another aspect of the present invention, in thepower-supply device, it is preferable that the controller turns off thefirst current blocker to be controlled when an overcurrent flows intothe first current blocker to be controlled and the second currentdirection to be uncontrolled that is different from the first currentdirection to be controlled is included, and turns off the second currentblocker to be controlled when an overcurrent flows into the secondcurrent blocker to be controlled and the first current direction to beuncontrolled that is different from the second current direction to becontrolled is included.

According to still another aspect of the present invention, in thepower-supply device, it is preferable that the first switch to becontrolled has a first short-circuit detector to be controlled, thefirst short-circuit detector being configured to detect a short circuitin the power-supply circuit, the second switch to be controlled has asecond short-circuit detector to be controlled, the second short-circuitdetector being configured to detect a short circuit in the power-supplycircuit, the first current detector to be controlled detects an amperageof a current flowing into the first current blocker to be controlled,the second current detector to be controlled detects an amperage of acurrent flowing into the second current blocker to be controlled, andthe controller controls turning on/off the first current blocker to becontrolled based on the amperage detected by the first current detectorto be controlled and a short-circuit result detected by the firstshort-circuit detector to be controlled, and controls turning on/off thesecond current blocker to be controlled based on the amperage detectedby the second current detector to be controlled and a short-circuitresult detected by the second short-circuit detector to be controlled.

According to still another aspect of the present invention, in thepower-supply device, it is preferable that the first switch to becontrolled has a first short-circuit detector to be controlled, thefirst short-circuit detector being configured to detect a short circuitin the power-supply circuit, the second switch to be controlled has asecond short-circuit detector to be controlled, the second short-circuitdetector being configured to detect a short circuit in the power-supplycircuit, the first current detector to be controlled detects an amperageof a current flowing into the first current blocker to be controlled,the second current detector to be controlled detects an amperage of acurrent flowing into the second current blocker to be controlled, andthe controller controls turning on/off the first current blocker to becontrolled based on either of the amperage detected by the first currentdetector to be controlled or a short-circuit result detected by thefirst short-circuit detector to be controlled, and controls turningon/off the second current blocker to be controlled based on either ofthe amperage detected by the second current detector to be controlled ora short-circuit result detected by the second short-circuit detector tobe controlled.

The above and other objects, features, advantages and technical andindustrial significance of this invention will be better understood byreading the following detailed description of presently preferredembodiments of the invention, when considered in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a configuration example of apower-supply device according to an embodiment;

FIG. 2 is a circuit diagram illustrating a configuration example of aswitch unit according to the embodiment;

FIG. 3 is a schematic diagram illustrating an example of a short circuitin the power-supply device according to the embodiment;

FIG. 4 is a schematic diagram illustrating a first operation exampleduring the short circuit in the power-supply circuit according to theembodiment;

FIG. 5 is a schematic diagram illustrating a second operation exampleduring the short circuit in the power-supply device according to theembodiment;

FIG. 6 is a block diagram illustrating a first operation example duringa short circuit in a switch unit according to a comparative example;

FIG. 7 is a block diagram illustrating a second operation example duringa short circuit of the switch unit according to the comparative example;

FIG. 8 is a block diagram illustrating a first operation example duringa short-circuit of the switch unit according to the embodiment;

FIG. 9 is a block diagram illustrating a second operation example duringa short circuit of the switch unit according to the embodiment;

FIG. 10 is a circuit diagram illustrating a configuration example of aswitch unit according to a first modification of the embodiment;

FIG. 11 is a circuit diagram illustrating a configuration example of aswitch unit according to a second modification of the embodiment;

FIG. 12 is a schematic diagram illustrating a configuration example of apower-supply device according to a third modification of the embodiment;

FIG. 13 is a schematic diagram illustrating a configuration example of apower-supply device according to a fourth modification of theembodiment; and

FIG. 14 is a schematic diagram illustrating a configuration example of apower-supply device according to a fifth modification of the embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments for conducting the present invention (embodiments) will bedescribed in detail with reference to the drawings. The presentinvention is not limited by the description of the followingembodiments. The components described below include one that is readilyconceived by those skilled in the art and one that is substantially thesame as those. Furthermore, the configurations described below can becombined as necessary. Various omissions, substitutions, or changes ofthe configurations can be conducted without departing from the subjectmatter of the present invention.

Embodiment

A power-supply device 1 according to an embodiment will be describedwith reference to the drawings. FIG. 1 is a schematic diagramillustrating a configuration example of the power-supply device 1according to the embodiment. FIG. 2 is a circuit diagram illustrating aconfiguration example of a switch unit 30 according to the embodiment.

As illustrated in FIG. 1, the power-supply device 1 is installed in avehicle and supplies power to a load unit 2 of the vehicle. The loadunit 2 is an electrical component that consumes relatively low power,such as electronic control units (ECUs) 2 a, 2 b and 2 c, or sensors 2d, 2 e, and 2 f, for example. The power-supply device 1 includes a powersupply 1 a, a power supply 1 b, and a power-supply circuit 1 c. Thepower supply 1 a is a storage battery that can storage direct-currentpower. The positive electrode of the power supply 1 a is coupled to thepower-supply circuit 1 c. The negative electrode of the power supply 1 ais coupled to the body of the vehicle for body-grounding. The powersupply 1 a supplies power to each load unit 2 coupled to thepower-supply circuit 1 c.

The power supply 1 b is a storage battery that can storagedirect-current power. The positive electrode of the power supply 1 b iscoupled to the power-supply circuit 1 c. The negative electrode of thepower supply 1 b is coupled to the body of the vehicle forbody-grounding. The power supply 1 b supplies power to each load unit 2coupled to the power-supply circuit 1 c.

The power-supply circuit 1 c is a circuit that carries a current and asignal. The power-supply circuit 1 c includes an electric-wire unit 10,a communication wire 20, and a plurality of switch units 30.

The electric-wire unit 10 is a conductive wire that carries a current.The electric-wire unit 10 has two current paths 11 and 12. One end ofthe current path 11 is coupled to the positive electrode of the powersupply 1 a, and the other end is coupled to the positive electrode ofthe power supply 1 b. The current path 12 has a path length that issubstantially the same as that of the current path 11. One end of thispath is coupled to the positive electrode of the power supply 1 a, andthe other end is coupled to the positive electrode of the power supply 1b. The current paths 11 and 12 are formed in a circular shape (ringshape). That is, the current paths 11 and 12 form a circular closecircuit. The electric-wire unit 10 carries a current of the powersupplied from the power supplies 1 a and 1 b to each load unit 2 via thecircular current paths 11 and 12 and other elements. Even if the numberof load units 2 increases, this enables the electric-wire unit 10 tosupply power to each load unit 2 via the shortest path without extensionof the current paths 11 and 12. In the electric-wire unit 10, thisprevents the weight of the electric-wire unit 10 and a space for routingthe electric-wire unit 10 from increasing.

The communication wire 20 is a conductive wire that carries a signal.The communication wire 20 couples the switch units 30 so as to mutuallycommunicate. The communication wire 20 carries a signal output from theswitch units 30.

The switch unit 30 is a branch switch that passes or blocks a currentflowing into the load unit 2. The switch units 30 are provided for theelectric-wire unit 10 and pass or block the current flowing into eachload unit 2 via the electric-wire unit 10. As illustrated in FIG. 2, theswitch unit 30 includes a control power supply (5 V power supply inFIG. 1) 31, a communication integrated circuit (IC) 32, a switch SW1, aswitch SW2, and a junction 35, and a CPU 36.

The 5 V power supply 31 supplies a power supply having a voltage of 5 V.The 5 V power supply 31 is coupled to the junction 35 on a connectingwire Lf described below, which couples a FET Q1 and a FET Q2. Apower-supply voltage VB of the power supply 1 a or the power supply 1 bis applied to this power supply. The 5 V power supply 31 transforms theapplied power-supply voltage VB to a voltage of 5 V. The 5 V powersupply 31, which is coupled to the CPU 36, supplies power of thetransformed 5 V voltage to the CPU 36.

The communication IC 32 can communicate with the communication IC 32 ofanother switch unit 30. The communication IC 32, which is coupled to theCPU 36 and the communication wire 20, transmits a signal output from theCPU 36 to the communication IC32 of another switch unit 30 via thecommunication wire 20. Furthermore, the communication IC 32 receives asignal output from the communication IC 32 of another switch unit 30 viathe communication wire 20 and outputs the received signal to the CPU 36.The communication IC 32 receives, for example, a first current direction(first current direction to be uncontrolled), which is the direction ofa current flowing into the FET Q1 of another switch unit 30 and a secondcurrent direction (second current direction to be uncontrolled), whichis the direction of a current flowing into the FET Q2 of another switchunit 30. The communication IC 32 of a certain switch unit 30 receives,for example, the first current direction of a current flowing into theFET Q1 of an adjacent switch unit 30 and the second current direction ofa current flowing into the FET Q2 of the adjacent switch unit 30.

The switch SW1 includes an intelligent power device (IPD) 33. The IPD 33is what is called an intelligent power device, and includes the FET Q1,a current sensor 33 a, and a driving unit 33 b.

The FET Q1 passes or blocks a current. For example, the FET Q1 is anN-channel-type metal-oxide-semiconductor (MOS) FET. The drain terminalof the FET Q1 is coupled to the drain terminal of the FET Q2. The sourceterminal of the FET Q1 is coupled to the adjacent switch unit 30. Thegate terminal of the FET Q1 is coupled to the driving unit 33 b. The FETQ1 has a body diode D1. The cathode terminal of the body diode D1 iscoupled to the side of the load unit 2. The anode terminal of the bodydiode D1 is coupled to the side of the adjacent switch unit 30. The FETQ1 is turned on/off by the driving unit 33 b. The FET Q1 passes acurrent flowing from one side of the electric-wire unit 10 to anotherside thereof when turned on by the drive unit 33 b, and blocks thecurrent flowing from one side of the electric-wire unit 10 to anotherside thereof when turned off by the drive unit 33 b.

The current sensor 33 a outputs the current flowing into the FET Q1. Thecurrent sensor 33 a includes a FET Q3. The drain terminal of the FET Q3is coupled to the drain terminal of the FET Q1. The source terminal ofthe FET Q3 is coupled to a ground via a current detection resistance R1.The gate terminal of the FET Q3 is coupled to the driving unit 33 b. Thecurrent sensor 33 a is coupled to the CPU 36 from a point between thesource terminal of the FET Q3 and the current detection resistance R1.The FET Q3 is turned on/off by the driving unit 33 b. The FET Q3 passesa current having a ratio determined relative to the current flowing intothe FET Q1 as a current flowing from the drain terminal side of the FETQ1 into the current detection resistance R1 when turned on by thedriving unit 33 b, and blocks the current flowing from the drainterminal side of the FET Q1 into the current detection resistance R1when turned off by the driving unit 33 b. The current sensor 33 ainputs, to the CPU 36, a voltage determined by the current flowing fromthe FET Q3 into the current detection resistance R1 and the currentdetection resistance R1 as a detected value of the current value.

The driving unit 33 b drives the FETs Q1 and Q3. The driving unit 33 bis coupled to the CPU 36, and the CPU36 outputs a command signal forturning on or off the FETs Q1 and Q3 to this unit. The driving unit 33 bturns on the FETs Q1 and Q3 when an on command signal is output from theCPU 36, and turns off the FETs Q1 and Q3 when an off command signal isoutput from CPU36.

The switch SW2 includes an IPD 34. The IPD 34 includes a FET Q2, acurrent sensor 34 a, and a driving unit 34 b. The FET Q2 passes orblocks a current. For example, the FET Q2 is an N-channel-type MOSFET.The drain terminal of the FET Q2 is coupled to the drain terminal of theFET Q1. The source terminal of the FET Q2 is coupled to an adjacentswitch unit 30. The gate terminal of the FET Q2 is coupled to thedriving unit 34 b. The FET Q2 has a body diode D2. The cathode terminalof the body diode D2 is coupled to the side of the load unit 2. Theanode terminal of the body diode D2 is coupled to the side of theadjacent switch unit 30. The FET Q2 is turned on/off by the driving unit34 b. The FET Q2 passes a current flowing from another side of theelectric-wire unit 10 into one side thereof when turned on by thedriving unit 34 b, and blocks the current flowing from another side ofthe electric-wire unit 10 into one side thereof when turned off by thedriving unit 34 b.

The current sensor 34 a outputs the current flowing into the FET Q2. Thecurrent sensor 34 a includes a FET Q4. The drain terminal of the FET Q4is coupled to the drain terminal of the FET Q2. The source terminal ofthe FET Q4 is coupled to the ground via a current detection resistanceR2. The gate terminal of the FET Q4 is coupled to the driving unit 34 b.The current sensor 34 a is coupled to the CPU 36 from a point betweenthe source terminal of the FET Q4 and the current detection resistanceR2. The FET Q4 is turned on/off by the driving unit 34 b. The FET Q4passes a determined ratio of a current relative to the current flowinginto the FET Q2 as a current flowing from the drain terminal side of theFET Q2 into the current detection resistance R2 when turned on by thedriving unit 34 b, and blocks the current flowing from the drainterminal side of the FET Q2 into the current detection resistance R2when turned off by the driving unit 34 b. The current sensor 34 ainputs, to the CPU 36, a voltage determined by the current flowing fromthe FET Q4 into the current detection resistance R2 and the currentdetection resistance R2 as a detected value of the current value.

The driving unit 34 b drives the FETs Q2 and Q4. The driving unit 34 bis coupled to the CPU 36, and the CPU 36 outputs a command signal forturning on or off the FETs Q2 and Q4 to this unit. The driving unit 34 bturns on the FETs Q2 and Q4 when an on command signal is output from theCPU 36, and turns off the FETs Q2 and Q4 when an off command signal isoutput from the CPU 36.

The junction 35 is provided at a point between the FET Q1 and the FETQ2. The junction 35 is provided on the connecting wire Lf, which couplesthe drain terminal of the FET Q1 to the drain terminal of the FET Q2.The load unit 2 is coupled to the junction 35.

The CPU 36 controls the FETs Q1 to Q4. The CPU 36 outputs, to thedriving unit 33 b, the command signal for turning on or off the FETs Q1and Q3 based on the current output from the current sensor 33 a. The CPU36 outputs, to the driving unit 34 b, the command signal for turning onor off the FETs Q2 and Q4 based on the current output from the currentsensor 34 a.

Specifically, the CPU 36 detects the amperage of the current flowinginto the FET Q1 based on the current output from the current sensor 33a. The CPU 36 compares, for example, the output current output from thecurrent sensor 33 a with a predetermined threshold, and determines thatan overcurrent flows into the FET Q1 when the output current is greaterthan or equal to the threshold. Furthermore, the CPU 36 detects thefirst current direction, which is the direction of the current flowinginto the FET Q1, based on the output current output from the currentsensor 33 a. For example, when a current flows in the direction from thedrain terminal to the source terminal of the FET Q1, an output voltagefrom the current sensor 33 a is positive and the CPU 36 determines thatthe current direction is a positive direction. When a current flows inthe direction from the source terminal to the drain terminal of the FETQ1, the output from the current sensor 33 a to the CPU 36 is 0 V. Inthis case, the CPU 36 determines whether the current flows toward anegative direction or whether the passed current is 0 A, in conjunctionwith current information of the adjacent switch unit 30.

Similarly, the CPU 36 detects the amperage of the current flowing intothe FET Q2 based on the current output from the current sensor 34 a. TheCPU 36 compares, for example, the output current output from the currentsensor 34 a with a predetermined threshold, and determines that anovercurrent flows into the FET Q2 when the output current is greaterthan or equal to the threshold. Furthermore, the CPU 36 detects thesecond current direction, which is the direction of the current flowinginto the FET Q2, based on the output current output from the currentsensor 34 a. For example, when a current flows in the direction from thedrain terminal to the source terminal of the FET Q2, an output voltagefrom the current sensor 34 a is positive and the CPU 36 determines thatthe current direction is a positive direction. When a current flows inthe direction from the source terminal to the drain terminal of the FETQ2, the CPU 36 knows that the output from the current sensor 34 a is 0V. In this case, the CPU 36 determines whether the current flows towardthe negative direction or whether the passed current is 0 A, inconjunction with current information of the adjacent switch unit 30.

The CPU36 turns off the own FET Q1 based on the amperage and the firstcurrent direction of the FET Q1 (FET Q1 to be controlled) of the ownswitch unit 30 as well as the second current direction of the FET Q2(FET Q2 to be uncontrolled) of another switch unit 30. That is, the CPU36 turns off the FET Q1 to be controlled based on the amperage of theFET Q1 to be controlled, the first current direction of the FET Q1 to becontrolled, and the second current direction of the FET Q2 to beuncontrolled. Here, the FET Q1 to be controlled is the FET Q1 that isincluded in the same switch unit 30 as a certain CPU 36 and is a targetcontrolled by the CPU36. The FET Q2 to be uncontrolled is the FET Q2that is included in the switch unit 30 different from a certain CPU 36(for example, the adjacent switch unit 30) and is not a targetcontrolled by the CPU36. For example, between adjacent switch units 30,when an overcurrent flows into the FET Q1 to be controlled and the firstcurrent direction of the FET Q1 to be controlled and the second currentdirection of the FET Q2 to be uncontrolled are different, the CPU36determines that a short circuit has occurred and turns off the FET Q1 tobe controlled.

Similarly, the CPU36 turns off the own FET Q2 based on the amperage andthe second current direction of the FET Q2 (FET Q2 to be controlled) ofthe own switch unit 30 as well as the first current direction of the FETQ1 (FET Q1 to be uncontrolled) of another switch unit 30. That is, theCPU36 turns off the FET Q2 to be controlled based on the amperage of theFET Q2 to be controlled, the second current direction of the FET Q2 tobe controlled, and the first current direction of the FET Q1 to beuncontrolled. For example, between adjacent switch units 30, when anovercurrent flows into the FET Q2 to be controlled and the secondcurrent direction of the FET Q2 to be controlled and the first currentdirection of the FET Q1 to be uncontrolled are different, the CPU 36determines that a short circuit has occurred and turns off the FET Q2 tobe controlled.

An operation example of the power-supply device 1 will now be described.For easy understanding of the description, an example in which the powersupply 1 a or the power supply 1 b supplies power to an ECU 2 a isdescribed. FIG. 3 is a schematic diagram illustrating an example of ashort circuit in the power-supply circuit 1 c according to theembodiment. FIG. 4 is a schematic diagram illustrating a first operationexample during the short circuit in the power-supply circuit 1 caccording to the embodiment. FIG. 5 is a schematic diagram illustratinga second operation example during the short circuit in the power-supplycircuit 1 c according to the embodiment.

For example, when the power-supply circuit 1 c is normal, thepower-supply device 1 supplies power from the power supply 1 a to theECU 2 a via the current path I1 or supplies power from the power supply1 b to the ECU 2 a via the current path I2, as illustrated in FIG. 1.For example, in the power-supply device 1, when a short circuit in thepower-supply circuit 1 c occurs at a point P1, short-circuit currents I3and I4 flow toward the point P1, as illustrated in FIG. 3. At this time,a switch unit 30 a detects an overcurrent and detects the currentdirection different from that of the adjacent switch unit 30 b, therebykeeping the own FET Q1 on and turning off the own FET Q2. This enablesthe switch unit 30 a to block the short-circuit current I3. The switchunit 30 b detects an overcurrent and detects the current directiondifferent from that of the adjacent switch unit 30 a, thereby turningoff the own FET Q1 and keeping the own FET Q2 on. This enables theswitch unit 30 b to block the short-circuit current I4. The switch units30 other than the switch units 30 a and 30 b keep their FETs Q1 and Q2on. As illustrated in FIG. 4, this enables the power-supply device 1 toelectrically isolate the point P1, which is a short-circuited point,from the power-supply circuit 1 c and supply power from the power supply1 a to the ECU 2 a via a current path I5. Note that, for example, whenthe short circuit in the power-supply circuit 1 c occurs at the point P1and the power supply 1 a has a failure, the power-supply device 1supplies power from the power supply 1 b to the ECU 2 a via a currentpath I6, as illustrated in FIG. 5.

An operation of the power-supply device 1 according to the embodimentwill now be described in detail with reference to a comparative example.FIG. 6 is a block diagram illustrating a first operation example duringa short circuit in a switch unit 30 r and other switch units accordingto the comparative example. FIG. 7 is a block diagram illustrating asecond operation example during a short circuit of the switch unit 30 rand other switch units according to the comparative example. FIG. 8 is ablock diagram illustrating a first operation example during a shortcircuit in the switch unit 30 a and other switch units according to theembodiment. FIG. 9 is a block diagram illustrating a second operationexample during a short circuit in the switch unit 30 a and other switchunits according to the embodiment.

The switch unit 30 r includes a blocker 91, a blocker 92, a currentmonitor 93, a communication unit 94, a load controller 95, and acontroller 96. The blocker 91 and the blocker 92 pass or block a currentflowing into an electric-wire unit 99. The current monitor 93 monitorsthe amperage and current direction of the current flowing through theelectric-wire unit 99. The communication unit 94 communicates via acommunication wire 98. The load controller 95 controls a load unit 97.The controller 96 controls the blockers 91 and 92 based on the result ofthe current monitor 93.

In a power-supply device 1Q according to the comparative example, when ashort circuit occurs at a point P2 located between the switch unit 30 rand the switch unit 30 t, short-circuit currents I7 and I8 flow towardthe point P2, as illustrated in FIG. 6. At this time, the switch unit 30r detects an overcurrent by using the current monitor 93 and detects thecurrent direction different from that of the adjacent switch unit 30 t,thereby keeping the own blocker 91 on and turning off the own blocker92. The switch unit 30 t detects an overcurrent by using the currentmonitor 93 and detects a current direction different from that of theadjacent switch unit 30 r, thereby turning off the own blocker 91 andkeeping the own blocker 92 on. This enables the power-supply device 1Qto electrically isolate the point P2, which is a short-circuited point,from the power-supply circuit and supply power to the load unit 97.

In the power-supply device 1Q according to the comparative example, whena short circuit occurs at a point P3 located between the load controller95 and the junction of the current monitor 93 and the blocker 92,short-circuit currents I9 and I10 flow toward the point P3, asillustrated in FIG. 7. At this time, the switch unit 30 r detects anovercurrent by using the current monitor 93 and detects a currentdirection different from that of the adjacent switch unit 30 t, therebykeeping the own blocker 91 on and turning off the own blocker 92. Inthis case, the short-circuit current I9 continue to flow even if theblocker 92 is turned off, and the switch unit 30 r thus may fail toelectrically isolate the point P3, which is a short-circuited point,from the power-supply circuit. Furthermore, no power is supplied to theswitch unit 30 r when the blockers 91 and 92 are turned off, and theswitch unit 30 r thus becomes inoperable even when the switch unit 30 ris normal.

In contrast, in the power-supply device 1 according to the embodiment,when a short circuit occurs at a point P4 located between the switchunit 30 a and the switch unit 30 b, short-circuit currents I11 and I12flow toward the point P4, as illustrated in FIG. 8. At this time, theswitch unit 30 a detects an overcurrent and detects a current direction(second current direction to be controlled) different from the currentdirection of the adjacent switch unit 30 b (first current direction tobe uncontrolled), thereby keeping the FET Q1 of the own IPD 33 on andturning off the FET Q2 of the own IPD 34. Furthermore, the switch unit30 b detects an overcurrent and detects a current direction (firstcurrent direction to be controlled) different from the current directionof the adjacent switch unit 30 a (second current direction to beuncontrolled), thereby turning off the FET Q1 of the own IPD 33 andkeeping the FET Q2 of the own IPD 34 on. Unlike the aforementioned case,the current directions of the switch units 30 other than the switchunits 30 a and 30 b are equal between adjacent switch units 30, so thatthese units keep their FETs Q1 and Q2 on. This enables the power-supplydevice 1 to electrically isolate the point P4, which is ashort-circuited point, from the power-supply circuit 1 c and supplypower from the power supplies 1 a and 1 b to the load unit 2.

In the power-supply device 1 according to the embodiment, when a shortcircuit occurs at a point P5 located between the load unit 2 and thejunction 35 of the IPD 33 and the IPD 34, short-circuit currents I13 andI14 flow toward the point P5, as illustrated in FIG. 9. At this time,the switch unit 30 a keeps the own FET Q1 on. This is because thedirection of a current flowing into the own FET Q1 (first currentdirection to be controlled) and the direction of a current flowing intothe FET Q2 of the adjacent switch unit 30 c (second current direction tobe uncontrolled) are the same direction. Furthermore, the switch unit 30a keeps the own FET Q2 on. This is because the direction of a currentflowing into the own FET Q2 (second current direction to be controlled)and the direction of the current flowing into the FET Q1 of the adjacentswitch unit 30 b (first current direction to be uncontrolled) are thesame direction.

The switch unit 30 b turns off own FET Q1. This is because the directionof the current flowing into the own FET Q1 (first current direction tobe controlled) and the direction the current flowing into the FET Q2 ofthe adjacent switch unit 30 a (the second current direction to beuncontrolled) are the same direction, while the direction of the currentflowing into the own FET Q1 (first current direction to be controlled)and the direction of a current flowing into the FET Q2 of the switchunit 30 c adjacent to the adjacent one (two units away) (second currentdirection to be uncontrolled) are different.

Similarly, the switch unit 30 c turns off the own FET Q2. This isbecause the direction the current flowing into the own FET Q2 (secondcurrent direction to be controlled) and the direction of the currentflowing into the FET Q1 of the adjacent switch unit 30 a (first currentdirection to be uncontrolled) are the same direction, while thedirection of the current flowing into the own FET Q2 (second currentdirection to be controlled) and the direction of the current flowinginto the FET Q1 of the switch unit 30 b adjacent to the adjacent one(two units away) (first current direction to be uncontrolled) aredifferent. In this way, each switch unit 30 turns off the own FETs Q1and Q2 based on the directions of the currents into the own FETs Q1 andQ2 as well as the directions of the currents into the FETs Q1 and Q2 ofthe adjacent switch unit 30. Even if the short circuit occurs at thepoint P5 located between the load unit 2 and the junction 35 of the IPD33 and the IPD 34, this enables the power-supply device 1 toelectrically isolate the short-circuited point P5 from the power-supplycircuit 1 c and supply power from the power supplies 1 a and 1 b toother load units 2.

The power-supply device 1Q according to the comparative examplesupplies, via the switch unit 30 r and other switch units, power to theload unit 97 that consumes high power, so that installing the multipleswitch units 30 r, 30 s, 30 t, and other switch units result in anincreased current flowing into the electric-wire unit 99. Thus, theelectric-wire unit 99 of the power-supply device 1Q must be thickened inorder that the blockers 91 and 92 can support a large current.

In contrast, the power-supply device 1 according to the embodimentsupplies, via the switch unit 30, power to the load unit 2 that consumeslow power, such as an ECU or a sensor, so that a current flowing intothe electric wire unit 10 can be lower than that of the power-supplydevice 1Q according to the comparative example. In the power-supplydevice 1 according to the embodiment, this enables an electric-wire unitof the electric-wire unit 10 to be thin and enables devices that supportsuch a low current to be used as the IPDs 33 and 34, thereby preventingan increase in an installing space and an increase in a production cost.

The power-supply device 1Q according to the comparative example may failto supply power to the controller 96 when the blockers 91 and 92 areoff. In contrast, the power-supply device 1 according to the embodimenthas the body diode D1 of the FET Q1 and the body diode D2 of the FET Q2,which are disposed in a direction where the CPU 36 is energized, andthus supplies, whether the FETs Q1 and Q2 are on or off, power to theCPU 36 when the switch unit 30 is coupled to the power supplies 1 a and1 b.

As above, the power-supply device 1 according to the embodiment includesthe power supplies 1 a and 1 b, the power-supply circuit 1 c, and theCPU 36. The power supplies 1 a and 1 b supply power. The power-supplycircuit 1 c is coupled to the power supplies 1 a and 1 b, and includesthe switch units 30. The switch units 30 pass or block a current of thepower supplied from the power supplies 1 a and 1 b. The CPU 36 controlsturning on/off the switches SW1 and SW2 of the switch unit 30 andcontrols the power-supply circuit 1 c. The switch units 30 include theswitch SW1, the switch SW2, and the junction 35. The switch SW1 has theFET Q1 and the current sensor 33 a. The FET Q1 passes or blocks acurrent flowing from one side in the power-supply circuit 1 c. Thecurrent sensor 33 a detects a current flowing into the FET Q1. Theswitch SW2 has the FET Q2 and the current sensor 34 a. The FET Q2 iscoupled to the FET Q1, and passes or blocks a current flowing fromanother side in the power-supply circuit 1 c. The current sensor 34 adetects a current flowing into the FET Q2. The junction 35 couples theload unit 2 at a point between the FET Q1 and the FET Q2. In each of theswitch units 30, the CPU 36 controls the corresponding switch unit 30 ofthe power-supply circuit 1 c based on the detection result detected bythe corresponding current sensors 33 a and 34 a.

When a short circuit occurs in the power-supply circuit 1 c, thisconfiguration enables the power-supply device 1 to block the SW1 and SW2of the switch unit 30 associated with the short-circuit point andenergize the SW1 and SW2 of the other switch units 30. When a shortcircuit occurs in the power-supply circuit 1 c, this enables thepower-supply device 1 to electrically isolates the short-circuit pointfrom the power-supply circuit 1 c to close a circuit other than theshort-circuit point and supply power to each load unit 2 coupled to theclosed circuit. This improves the fault tolerance of the power-supplydevice 1.

In the power-supply device 1, the switch unit 30 to be controlledincludes the communication IC 32 that can communicate with the switchunit 30 to be uncontrolled. The current sensor 33 a to be controlleddetects the amperage of the current flowing into the FET Q1 to becontrolled and the first current direction to be controlled, which isthe direction of the current flowing into the FET Q1 to be controlled.The current sensor 34 a to be controlled detects the amperage of thecurrent flowing into the FET Q2 to be controlled and the second currentdirection to be controlled, which is the direction of the currentflowing into the FET Q2 to be controlled. The communication IC 32 to becontrolled receives the first current direction to be uncontrolled,which is the direction of the current flowing into the FET Q1 to beuncontrolled of the switch unit 30 to be uncontrolled and the secondcurrent direction to be uncontrolled, which is the direction of thecurrent flowing into the FET Q2 to be uncontrolled of the switch unit 30to be uncontrolled. The CPU 36 controls turning on/off the FET Q1 to becontrolled based on the amperage of the FET Q1 to be controlled, thefirst current direction to be controlled, and the second currentdirection to be uncontrolled, and controls turning on/off the FET Q2 tobe controlled based on the amperage of the FET Q2 to be controlled, thesecond current direction to be controlled, and the first currentdirection to be uncontrolled. This configuration enables thepower-supply device 1 to determine a short circuit based on thedirections where the currents flows and their amperages, turn off theFETs Q1 and Q2 based on the determination results, and block a currentflowing into the short-circuit point in the power-supply circuit 1 c.

When an overcurrent flows into the FET Q1 to be controlled and thesecond current direction of the FET Q2 to be uncontrolled that isdifferent from the first current direction of the FET Q1 to becontrolled is included, the CPU36 of the power-supply device 1 turns offthe FET Q1 to be controlled. When an overcurrent flows into the FET Q2to be controlled and the first current direction of the FET Q1 to beuncontrolled that is different from the second current direction of theFET Q2 to be controlled is included, the CPU36 turns off the FET Q2 tobe controlled. If the current directions are different when anovercurrent flows, this configuration enables the power-supply device 1to turn off the FETs Q1 and Q2 to be controlled and block a currentflowing into the short-circuit point in the power-supply circuit 1 c.

Modification

Modifications of the Embodiment will now be described. FIG. 10 is acircuit diagram illustrating a configuration example of a switch unit30A according to a first modification of the embodiment. Note that, inthe following modifications, the same number is referred to thecomponents equal to those of the embodiment and the detailed descriptionis omitted. The switch unit 30A is different from the switch unit 30according to the embodiment in that this unit includes a short-circuitdetector. As illustrated in FIG. 10, the switch unit 30A includes the 5V power supply 31, the switch SW1, the switch SW2, the junction 35, andthe CPU36. The switch SW1 has the IPD 33 and a first short-circuitdetector 33 c. The switch SW2 has the IPD 34 and a second short-circuitdetector 34 a.

The first short-circuit detector 33 c detects a short circuit in thepower-supply circuit 1 c. The first short-circuit detector 33 c includesan electric wire L2, through which power is supplied from the sourceterminal side of the FET Q1 via a resistance R3. The electric wire L2 iscoupled to the CPU 36. When no short circuit occurs on the sourceterminal side of the FET Q1, the first short-circuit detector 33 coutputs a voltage equal to the power-supply voltage VB to the CPU 36. Incontrast, when a short circuit occurs on the source terminal side of theFET Q1, the first short-circuit detector 33 c outputs a voltage equal to0 V to the CPU 36. The CPU 36 determines a short circuit based on thevoltage output from the first short-circuit detector 33 c to becontrolled. For example, the CPU 36 determines that no short circuitoccurs, when the first short-circuit detector 33 c to be controlledoutputs the voltage equal to the power-supply voltage VB. The CPU 36determines that a short circuit occurs on the source terminal side ofthe FET Q1 to be controlled, when the first short-circuit detector 33 cto be controlled outputs the voltage equal to 0 V.

The CPU 36 turns off the FET Q1 to be controlled based on theshort-circuit result detected by the first short-circuit detector 33 cto be controlled and the amperage detected by the current sensor 33 a tobe controlled. For example, the CPU 36 turns off the FET Q1 to becontrolled when an overcurrent is detected by the current sensor 33 a tobe controlled and a short circuit is detected by the first short-circuitdetector 33 c to be controlled. In contrast, the CPU 36 does not turnoff the FET Q1 to be controlled when no overcurrent is detected by thecurrent sensor 33 a to be controlled or no short circuit is detected bythe first short-circuit detector 33 c to be controlled.

Similarly, the second short-circuit detector 34 c detects a shortcircuit in the power-supply circuit 1 c. The second short-circuitdetector 34 c includes an electric wire L4, through which power issupplied from the source terminal side of the FET Q2 via a resistanceR5. The electric wire L4 is coupled to the CPU 36. When no short circuitoccurs on the source terminal side of the FET Q2, the secondshort-circuit detector 34 c outputs a voltage equal to the power-supplyvoltage VB to the CPU 36. When a short circuit occurs on the sourceterminal side of the FET Q1, the second short-circuit detector 34 coutputs a voltage equal to 0 V to the CPU 36. The CPU 36 determines ashort circuit based on the voltage output from the second short-circuitdetector 34 c to be controlled. For example, the CPU 36 determines thatno short circuit occurs, when the second short-circuit detector 34 c tobe controlled outputs the voltage equal to the power-supply voltage VB.The CPU 36 determines that a short circuit occurs, when the secondshort-circuit detector 34 c to be controlled outputs the voltage equalto 0 V.

The CPU 36 turns off the FET Q2 based on the short-circuit resultdetected by the second short-circuit detector 34 c to be controlled andthe amperage detected by the current sensor 34 a to be controlled. Forexample, the CPU 36 turns off the FET Q2 to be controlled when anovercurrent is detected by the current sensor 34 a to be controlled anda short circuit is detected by the second short-circuit detector 34 c tobe controlled. The CPU 36 does not turn off the FET Q2 to be controlledwhen no overcurrent is detected by the current sensor 34 a to becontrolled or no short circuit is detected by the second short-circuitdetector 34 c to be controlled.

As above, in the switch unit 30A according to the first modification ofthe embodiment, the switch SW1 to be controlled has the firstshort-circuit detector 33 c to be controlled, which detects a shortcircuit in the power-supply circuit 1 c. The switch SW2 to be controlledhas the second short-circuit detector 34 c to be controlled, whichdetects a short circuit in the power-supply circuit 1 c. The currentsensor 33 a to be controlled detects the current flowing into the FET Q1to be controlled. The current sensor 34 a to be controlled detects theamperage of the current flowing into the FET Q2 to be controlled. TheCPU 36 turns off the FET Q1 to be controlled based on the amperagedetected by the current sensor 33 a to be controlled and theshort-circuit result detected by the first short-circuit detector 33 cto be controlled, and turns off the FET Q2 to be controlled based on theamperage detected by the current sensor 34 a to be controlled and theshort-circuit result detected by the second short-circuit detector 34 cto be controlled. If the switch unit 30A detects a short circuit when anovercurrent flows, this configuration enables this switch unit to turnoff the FETs Q1 and Q2 to be controlled and block a current flowing intothe short-circuit point in the power-supply circuit 1 c.

A switch unit 30B according to a second modification of the embodimentwill now be described. FIG. 11 is a circuit diagram illustrating aconfiguration example of the switch unit 30B according to the secondmodification of the embodiment. The switch unit 30B is different fromthe switch unit 30 according to the embodiment in that this unitincludes a short-circuit detector. As illustrated in FIG. 11, the switchunit 30B includes the switch SW1, the switch SW2, and the junction 35.The switch SW1 has the IPD 33, a first current-determining unit 37 a, afirst short-circuit detector 33 d, and an IPD controller 37 b. Theswitch SW2 has the IPD 34, a second current-determining unit 37 c, asecond short-circuit detector 34 d, and an IPD controller 37 d.

The first current-determining unit 37 a of the switch SW1 determines anovercurrent. The first current-determining determining unit 37 a has apower supply 37 e and a comparator 37 f. The power supply 37 e applies aconstant voltage. The power supply 37 e is coupled to a first inputterminal of the comparator 37 f and applies the constant voltage to thefirst input terminal. The current sensor 33 a is coupled to a secondinput terminal of the comparator 37 f and outputs the voltagecorresponding to an output current to the second input terminal. Theoutput terminal of the comparator 37 f is coupled to the gate terminalof a FET Q6 via a resistance R15. The comparator 37 f compares thevoltage corresponding to the output current output from the currentsensor 33 a with the applied voltage applied by the power supply 37 e.When the voltage corresponding to the output current is greater than orequal to the applied voltage, the comparator 37 f determines that anovercurrent flows into the FET Q1 and turns on the FET Q6 of the IPDcontroller 37 b to turn off the FET Q1. In contrast, when the voltagecorresponding to the output current is less than the applied voltage,the comparator 37 f determines that no overcurrent flows into the FETQ1, and turns off the FET Q6 of the IPD controller 37 b to turn on theFET Q1.

The first short-circuit detector 33 d detects a short circuit in thepower-supply circuit 1 c. The first short-circuit detector 33 d has aFET Q5. The FET Q5 is a P-channel-type MOSFET. The drain terminal of theFET Q5 is coupled to the gate terminal of the FET Q6 via a resistanceR9. The source terminal of the FET Q5 is coupled to the drain terminalof the FET Q1 and coupled to the source terminal of the FET Q1 via aresistance R8. The gate terminal of the FET Q5 is coupled to the sourceterminal of the FET Q1 via a resistance R7. When a short circuit occurson the source terminal side of the FET Q1, the first short-circuitdetector 33 d turns on the FET Q5. This causes the first short-circuitdetector 33 d to turn on the FET Q6 of the IPD controller 37 b to turnoff the FET Q1. When no short circuit occurs on the source terminal sideof the FET Q1, the first short-circuit detector 33 d turns off the FETQ5. This causes the first short-circuit detector 33 d to turn off theFET Q6 of the IPD controller 37 b to turn on the FET Q1.

The IPD controller 37 b controls the FET Q1. The IPD controller 37 b hasthe FET Q6. The FET Q6 is an N-channel-type MOSFET. The drain terminalof the FET Q6 is coupled to the IPD 33. The source terminal of the FETQ6 is coupled to the ground. The gate terminal of the FET Q6 is coupledto the first current-determining unit 37 a and the first short-circuitdetector 33 d. Specifically, the drain terminal of the FET Q6 is coupledto the driving unit 33 b. The gate terminal of the FET Q6 is coupled tothe output terminal of the comparator 37 f and the drain terminal of theFET Q5. The junction at a point between the drain terminal of the FET Q6and the driving unit 33 b is coupled to the connecting wire Lf via aresistance R10.

When the first current-determining unit 37 a to be controlled detects anovercurrent, the IPD controller 37 b turns off the FET Q1 to becontrolled by turning on the FET Q6 and blocks a current flowing intothis FET Q1 to be controlled. In contrast, when the firstcurrent-determining unit 37 a to be controlled detects no overcurrent,the IPD controller 37 b turns on the FET Q1 to be controlled by turningoff the FET Q6 and does not block the current flowing into this FET Q1to be controlled. When the first short-circuit detector 33 d to becontrolled detects a short circuit, the IPD controller 37 b turns offthe FET Q1 to be controlled by turning on the FET Q6 and blocks thecurrent flowing into this FET Q1 to be controlled. When the firstshort-circuit detector 33 d to be controlled detects no short circuit,the IPD controller 37 b turns on the FET Q1 to be controlled by turningoff the FET Q6 and does not block the current flowing into this FET Q1to be controlled. In this way, the switch unit 30B turns off the FET Q1to be controlled based on either of the overcurrent detected by thecurrent sensor 33 a to be controlled or the short-circuit resultdetected by the first short-circuit detector 33 d to be controlled.

The second current-determining unit 37 c of the switch SW2 determines anovercurrent. The second current-determining unit 37 c has a power supply37 g and a comparator 37 h. The power supply 37 g applies a constantvoltage. The power supply 37 g is coupled to a first input terminal ofthe comparator 37 h and applies the constant voltage to the first inputterminal. The current sensor 34 a is coupled to a second input terminalof the comparator 37 h and outputs a voltage corresponding to an outputcurrent to the second input terminal. The output terminal of thecomparator 37 h is coupled to the gate terminal of a FET Q8 via aresistance R16. The comparator 37 h compares the voltage correspondingto the output current output from the current sensor 34 a with theapplied voltage applied by the power supply 37 g. When the voltagecorresponding to the output current is greater than or equal to theapplied voltage, the comparator 37 f determines that an overcurrentflows into the FET Q2 and turns on the FET Q8 of the IPD controller 37 dto turn off the FET Q2. In contrast, when the voltage corresponding tothe output current is less than the applied voltage, the comparator 37 hdetermines that no overcurrent flows into the FET Q2, and turns off theFET Q8 of the IPD controller 37 d to turn on the FET Q2.

The second short-circuit detector 34 d detects a short circuit in thepower-supply circuit 1 c. The second short-circuit detector 34 d has aFET Q7. The FET Q7 is a P-channel-type MOSFET. The drain terminal of theFET Q7 is coupled to the gate terminal of the FET Q8 via a resistanceR13. The source terminal of the FET Q7 is coupled to the drain terminalof the FET Q2 and coupled to the source terminal of the FET Q2 via aresistance R12. The gate terminal of the FET Q7 is coupled to the sourceterminal of the FET Q2 via a resistance R11. When a short circuit occurson the source terminal side of the FET Q2, the second short-circuitdetector 34 d turns on the FET Q7. This causes the second short-circuitdetector 34 d to turn on the FET Q8 of the IPD controller 37 d to turnoff the FET Q2. When no short circuit occurs on the source terminal sideof the FET Q2, the second short-circuit detector 34 d turns off the FETQ7. This causes the second short-circuit detector 34 d to turn off theFET Q8 of the IPD controller 37 d to turn on the FET Q2.

The IPD controller 37 d controls the FET Q2. The IPD controller 37 d hasthe FET Q8. The FET Q8 is an N-channel-type MOSFET. The drain terminalof the FET Q8 is coupled to the IPD 34. The source terminal of the FETQ8 is coupled to the ground. The gate terminal of the FET Q8 is coupledto the second current-determining unit 37 c and the second short-circuitdetector 34 d. Specifically, the drain terminal of the FET Q8 is coupledto the driving unit 34 b. The gate terminal of the FET Q8 is coupled tothe output terminal of the comparator 37 h and the drain terminal of theFET Q7. The junction at a point between the drain terminal of the FET Q8and the driving unit 34 b is coupled to the connecting wire Lf via aresistance R14.

When the second current-determining unit 37 c to be controlled detectsan overcurrent, the IPD controller 37 d turns off the FET Q2 to becontrolled by turning on the FET Q8 and blocks a current flowing intothis FET Q2 to be controlled. In contrast, when the secondcurrent-determining unit 37 c to be controlled detects no overcurrent,the IPD controller 37 d turns on the FET Q2 to be controlled by turningon the FET Q8 and does not block this FET Q2 to be controlled. When thesecond short-circuit detector 34 d to be controlled detects a shortcircuit, the IPD controller 37 d turns off the FET Q2 to be controlledby turning on the FET Q8 and blocks the current flowing into this FET Q2to be controlled. When the second short-circuit detector 34 d to becontrolled detects no short circuit, the IPD controller 37 d turns onthe FET Q2 to be controlled by turning off the FET Q8 and does not blockthe current flowing into this FET Q2 to be controlled. In this way, theswitch unit 30B turns off the FET Q2 to be controlled based on either ofthe overcurrent detected by the current sensor 34 a to be controlled orthe short-circuit result detected by the second short-circuit detector34 d to be controlled.

As above, in the switch unit 30B according to the second modification ofthe embodiment, the switch SW1 to be controlled has the firstshort-circuit detector 33 d to be controlled, which detects a shortcircuit in the power-supply circuit 1 c. The switch SW2 to be controlledhas the second short-circuit detector 34 d to be controlled, whichdetects a short circuit in the power-supply circuit 1 c. The currentsensor 33 a to be controlled detects the amperage of the current flowinginto the FET Q1 to be controlled. The current sensor 34 a to becontrolled detects the amperage of the current flowing into the FET Q2to be controlled. The IPD controller 37 b turns off the FET Q1 to becontrolled based on either of the amperage detected by current sensor 33a to be controlled or the short-circuit result detected by the firstshort-circuit detector 33 d to be controlled. The IPD controller 37 dturns off the FET Q2 to be controlled based on either of the amperagedetected by current sensor 34 a to be controlled or the short-circuitresult detected by the second short-circuit detector 34 d to becontrolled. When an overcurrent flows, this configuration enables theswitch unit 30B to turn off the FETs Q1 and Q2 to be controlled andblock the current flowing into the power-supply circuit 1 c. When theswitch unit 30B detects a short circuit, this unit turns off the FETs Q1and Q2 to be controlled and blocks the current flowing into theshort-circuit point in the power-supply circuit 1 c.

The power-supply device 1A according to a third modification of theembodiment will now be described. FIG. 12 is a schematic diagramillustrating a configuration example of the power-supply device 1Aaccording to the third modification of the embodiment. In thepower-supply device 1A according to the third modification, the topologyof a power-supply circuit 1 d is different from that of the power-supplydevice 1 according to the embodiment. As illustrated in FIG. 12, thepower-supply device 1A according to the third modification includes thepower supply 1 a, the power supply 1 b, and the power-supply circuit 1d.

The power supply 1 a, the positive electrode of which is coupled to thepower-supply circuit 1 d and the negative electrode of which is coupledto the body of the vehicle for body-grounding, supplies power to eachload unit 2 of the power-supply circuit 1 d. The power supply 1 b, thepositive electrode of which is coupled to the power-supply circuit 1 dand the negative electrode of which is coupled to the body of thevehicle for body-grounding, supplies power to each load unit 2 of thepower-supply circuit 1 d.

The power-supply circuit 1 d includes the electric-wire unit 10, and theswitch units 30. The electric-wire unit 10 has one current path 11. Thiscurrent path 11, one end of which is coupled to the positive electrodeof the power supply 1 a and the other end of which is coupled to thepositive electrode of the power supply 1 b, is formed in a linear shape.The current path 11 carries a current of the power supplied from thepower supplies 1 a and 1 b. The switch units 30 are provided for thecurrent path 11, and pass or block a current flowing into each load unit2 via this current path 11.

As above, the power-supply circuit 1 d of the power-supply device 1Aaccording to the third modification has the current path 11 formed inthe linear shape. One end of the current path 11 is coupled to thepositive electrode of the power supply 1 a, and the other end is coupledto the positive electrode of the power supply 1 b. This configurationenables the power-supply device 1A to supply power to each load unit 2coupled to the current path 11.

A power-supply device 1B according to a fourth modification of theembodiment will now be described. FIG. 13 is a schematic diagramillustrating a configuration example of the power-supply device 1Baccording to the fourth modification of the embodiment. In thepower-supply device 1B according to the fourth modification, thetopology of a power-supply circuit 1 e is different from that of thepower-supply device 1 according to the embodiment. As illustrated inFIG. 13, the power-supply device 1B according to the fourth modificationincludes the power supply 1 a, the power supply 1 b, and thepower-supply circuit 1 e.

The power supply 1 a, the positive electrode of which is coupled to thepower-supply circuit 1 e and the negative electrode of which is coupledto the body of the vehicle for body-grounding, supplies power to eachload unit 2 of the power-supply circuit 1 e. The power supply 1 b, thepositive electrode of which is coupled to the power-supply circuit 1 eand the negative electrode of which is coupled to the body of thevehicle for body-grounding, supplies power to each load unit 2 of thepower-supply circuit 1 e.

The power-supply circuit 1 e includes the electric-wire unit 10 and theswitch units 30. The electric-wire unit 10 has a circular part 15 and aredundant part 16. The circular part 15 is formed in a circular shape bythe current paths 11 and 12. One end of the current path 11 is coupledto the positive electrode of the power supply 1 a, and the other end iscoupled to the positive electrode of the power supply 1 b. One end ofthe current path 12 is coupled to the positive electrode of the powersupply 1 a, and the other end is coupled to the positive electrode ofthe power supply 1 b. The current paths 11 and 12 form a circular closecircuit.

The redundant part 16 is provided inside the circular part 15 and isformed in a linear shape by the current paths 13 and 14. One end 13 a ofthe current path 13 is coupled at a point between adjacent switch units30, and the other end 13 b is coupled at a point between other adjacentswitch units 30. The current path 13 is provided with two switches 4.Each switch 4 passes or blocks a current flowing into the current path13.

The current path 14 is disposed by intersecting the current path 13inside the redundant part 16. One end 14 a of the current path 14 iscoupled at a point between adjacent switch units 30, and the other end14 b is coupled at a point between other adjacent switch units 30. Theends 14 a and 14 b of the current path 14 are coupled at pointsdifferent from one end 13 a and the other end 13 b of the current path13. The current path 14 is provided with two switches 4. Each switch 4passes or blocks a current flowing into the current path 14. The switchunits 30 are provided for the current paths 11 and 12 of the circularpart 15, and pass or block a current flowing into each load unit 2 viathe current paths 11 and 12.

As above, the power-supply circuit 1 e of the power-supply device 1Baccording to the fourth modification has the circular part 15 and theredundant part 16. The circular part 15 is formed in the circular shapeby the current paths 11 and 12. The redundant part 16 is provided insidethe circular part 15 and is formed in the linear shape by the currentpaths 13 and 14. Even if a failure such as any short circuit ordisconnection occurs in the circular part 15, this configuration enablesthe power-supply device 1B to supply power to each load unit 2 via theredundant port 16. This enables its fault tolerance to be improved.

A power-supply device 1C according to a fifth modification of theembodiment will now be described. FIG. 14 is a schematic diagramillustrating a configuration example of the power-supply device 1Caccording to the fifth modification of the embodiment. The power-supplydevice 1C according to the fifth modification is different from thepower-supply device 1 according to the embodiment in that each load unit(ECU, sensor) 2 is coupled to the junction 35 of the switch unit 30 viaa J/B6 as an electric junction box (junction box). The J/B6 distributespower supplied from the power supplies 1 a and 1 b to each load unit 2.In the power-supply device 1C according to the fifth modification, forexample, each load unit (sensor, ECU) 2 is coupled to the J/B6, and theJ/B6 is coupled to the junction 35 of the switch unit 30, as illustratedin FIG. 14. In this way, the J/B6 of the power-supply device 1C may becoupled to the junction 35 of the switch unit 30, and the load unit 2may be coupled to the J/B6.

Note that the above description provides the example where the CPU 36 isprovided inside each switch unit 30 for every switch unit 30, but is notlimited to this. The CPU 36 may be provided outside the switch unit 30as a common controller. For example, one or more CPUs 36 may be providedoutside the switch unit 30 as a common controller, and the CPUs 36 maycontrol the switch units 30.

The description provides the example where the FETs Q1 to Q8 areMOSFETs, but is not limited to this. They may be other switch elements,such as insulated gate bipolar transistors (IGBTs).

The description provides the example where the power supply 1 a is astorage battery that can store direct-current power, but is not limitedto this. This power supply may be any one that can supply power, and maybe a generator, such as an alternator, or a voltage converter, such as aDC/DC converter, for example.

The description gives the example where the switch SW1 includes the IPD33, but is not limited to this. It may be any other configurations thatcan detect a short circuit to block a current. For example, the switchSW1 may include a mechanical relay and a current sensor, and may detecta short circuit based on the detection result of the current sensor andblock a current by using the mechanical relay. The switch SW2 is alsosimilar.

In each of the switch units, the power-supply device according to theembodiment controls the power-supply circuit based on the detectionresults detected by the first and second current detectors and thusenables its fault tolerance to faults, such as a short circuit to beimproved.

Although the invention has been described with respect to specificembodiments for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teaching herein setforth.

What is claimed is:
 1. A power-supply device comprising: a power supplythat supplies power; a power-supply circuit that is a circuit coupled tothe power supply and includes a plurality of switch units, the switchunits passing or blocking a current of the power supplied from the powersupply; and a controller that controls turning on/off the switch unitsand controls the power-supply circuit; wherein each of the switch unitsinclude: a first switch having a first current blocker that passes orblocks a current flowing from one side in the power-supply circuit and afirst current detector that detects a current flowing into the firstcurrent blocker; a second switch having a second current blocker that iscoupled to the first current blocker and passes or blocks a currentflowing from another side in the power-supply circuit and a secondcurrent detector that detects a current flowing into the second currentblocker; and a junction that couples a load unit at a point between thefirst current blocker and the second current blocker, and in each of theswitch units, the controller controls the power-supply circuit based ondetection results detected by the corresponding first current detectorand the second current detector, the switch unit to be controlledincludes a communication unit to be controlled that is capable ofcommunicating with the switch unit to be uncontrolled, the first currentdetector to be controlled detects an amperage of the current flowinginto the first current blocker to be controlled, and a first currentdirection to be controlled that is a direction of the current flowinginto the first current blocker to be controlled, the second currentdetector to be controlled detects an amperage of the current flowinginto the second current blocker to be controlled, and a second currentdirection to be controlled that is a direction of the current flowinginto the second current blocker to be controlled, the communication unitto be controlled receives a first current direction to be uncontrolledthat is the direction of the current flowing into the first currentblocker of the switch unit to be uncontrolled, and a second currentdirection to be uncontrolled that is the direction of the currentflowing into the second current blocker of the switch unit to beuncontrolled, and the controller controls turning on/off the firstcurrent blocker to be controlled based on the amperage of the firstcurrent blocker to be controlled, the first current direction to becontrolled, and the second current direction to be uncontrolled, andcontrols turning on/off the second current blocker to be controlledbased on the amperage of the second current blocker to be controlled,the second current direction to be controlled, and the first currentdirection to be uncontrolled.
 2. The power-supply device according toclaim 1, wherein the controller turns off the first current blocker tobe controlled when an overcurrent flows into the first current blockerto be controlled and the second current direction to be uncontrolledthat is different from the first current direction to be controlled isincluded, and turns off the second current blocker to be controlled whenan overcurrent flows into the second current blocker to be controlledand the first current direction to be uncontrolled that is differentfrom the second current direction to be controlled is included.
 3. Apower-supply device comprising: a power supply that supplies power; apower-supply circuit that is a circuit coupled to the power supply andincludes a plurality of switch units, the switch units passing orblocking a current of the power supplied from the power supply; and acontroller that controls turning on/off the switch units and controlsthe power-supply circuit; wherein each of the switch units include: afirst switch having a first current blocker that passes or blocks acurrent flowing from one side in the power-supply circuit and a firstcurrent detector that detects a current flowing into the first currentblocker; a second switch having a second current blocker that is coupledto the first current blocker and passes or blocks a current flowing fromanother side in the power-supply circuit and a second current detectorthat detects a current flowing into the second current blocker; and ajunction that couples a load unit at a point between the first currentblocker and the second current blocker, in each of the switch units, thecontroller controls the power-supply circuit based on detection resultsdetected by the corresponding first current detector and the secondcurrent detector, the first switch to be controlled has a firstshort-circuit detector to be controlled, the first short-circuitdetector being configured to detect a short circuit in the power-supplycircuit, the second switch to be controlled has a second short-circuitdetector to be controlled, the second short-circuit detector beingconfigured to detect a short circuit in the power-supply circuit, thefirst current detector to be controlled detects an amperage of thecurrent flowing into the first current blocker to be controlled, thesecond current detector to be controlled detects an amperage of thecurrent flowing into the second current blocker to be controlled, andthe controller controls turning on/off the first current blocker to becontrolled based on the amperage detected by the first current detectorto be controlled and a short-circuit result detected by the firstshort-circuit detector to be controlled, and controls turning on/off thesecond current blocker to be controlled based on the amperage detectedby the second current detector to be controlled and a short-circuitresult detected by the second short-circuit detector to be controlled.4. A power-supply device comprising: a power supply that supplies power;a power-supply circuit that is a circuit coupled to the power supply andincludes a plurality of switch units, the switch units passing orblocking a current of the power supplied from the power supply; and acontroller that controls turning on/off the switch units and controlsthe power-supply circuit; wherein each of the switch units include: afirst switch having a first current blocker that passes or blocks acurrent flowing from one side in the power-supply circuit and a firstcurrent detector that detects a current flowing into the first currentblocker; a second switch having a second current blocker that is coupledto the first current blocker and passes or blocks a current flowing fromanother side in the power-supply circuit and a second current detectorthat detects a current flowing into the second current blocker; and ajunction that couples a load unit at a point between the first currentblocker and the second current blocker, in each of the switch units, thecontroller controls the power-supply circuit based on detection resultsdetected by the corresponding first current detector and the secondcurrent detector, the first switch to be controlled has a firstshort-circuit detector to be controlled, the first short-circuitdetector being configured to detect a short circuit in the power-supplycircuit, the second switch to be controlled has a second short-circuitdetector to be controlled, the second short-circuit detector beingconfigured to detect a short circuit in the power-supply circuit, thefirst current detector to be controlled detects an amperage of thecurrent flowing into the first current blocker to be controlled, thesecond current detector to be controlled detects an amperage of thecurrent flowing into the second current blocker to be controlled, andthe controller controls turning on/off the first current blocker to becontrolled based on either of the amperage detected by the first currentdetector to be controlled or a short-circuit result detected by thefirst short-circuit detector to be controlled, and controls turningon/off the second current blocker to be controlled based on either ofthe amperage detected by the second current detector to be controlled ora short-circuit result detected by the second short-circuit detector tobe controlled.